Tunable high frequency tube



Oct. 16, 1962 J. I. SOLOMON TUNABLE HIGH FREQUENCY TUBE Filed Aug. 22,1960 INV EN TOR.

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3,059,139 TUNABLE HIGH FREQUENCY TUBE Jack I. Solomon, Redwood City,Calif assignor to Varian Associates, Palo Alto, Calif a corporation ofCalifornia Filed Aug. 22, 1960, Ser. No. 51,045 Clm'ms. (Cl. 315-522)This invention relates generally to ultra-high frequency devices and hasreference, more particularly, to novel, tunable, ultra-high frequencyreflex klystrons.

Ultra-high frequency reflex klystrons employing a cavity resonator andelectron beam reflector as heretofore constructed have utilized externaltuning cavities where environments were severe and extreme frequencystability was required, as for example, for use in missile, airborneradar and similar applications. The conventional gn'd gap tunedklystrons have a somewhat wider mechanical tuning range than externalcavity tuned tubes; however, they were not as stable as the externalcavity tuned tubes.

It is, therefore, the principal object of the present invention toprovide a novel reflex klyston tube which is grid gap tuned yet has thefrequency stability in severe conditions of environment as does a fixedtuned klystron employing an external tuning cavity.

The main feature of the present invention is to provide a compressiblemain body portion which acts upon the grid headers to change therelative position of the grids and thereby cause the frequency to shift.

Another feature of the present invention is the provision of a ruggedexternal tuning device which provides fine tuning and positive locking.

Other features and advantages of the present invention will becomeapparent from a perusal of the following specification taken inconnection with the following drawings wherein the invention isembodied.

In the drawings, FIG. 1 is a perspective view of a reflex klystronshowing the external tuning means as utilized,

FIG. 2 is a part longitudinal sectional view of a reflex klystron of thetype utilized in the present invention,

FIG. 3 is a part sectional view taken along lines 33 of FIG. 2, and

FIG. 4 is an enlarged sectional view showing the utilization of thepresent invention in the cavity resonator of a reflex klystron.

Referring now to the drawings, the reference number 11 designates ahousing or bulb portion of the novel tube incorporating this inventionwithin which the cathode 12 is contained. Surrounding cathode 12 is asupport assembly 13 which also serves as a focus electrode for theelectron beam emitted from the cathode 12.

A hollow cylindrical anode drift tube 14 having a slightly conical ordished, washer-like header 15 assembled thereon as by brazing isinserted within a main body member 16, a U-shaped metal member having anaperture bored through the base of the U to form the central bodyportion of the present klystron. Housing portion 11 for the cathodeassembly is secured as by brazing into one end of the aperture in mainbody portion member 16.

One end of the hollow drift tube 14 is provided with an acceleratinggrid 14' and the other end has a resonator grid 17 mounted thereon andspaced from an opposed grid 18 mounted on a conical dish-shaped headerring 19 secured to the inner end of a reflector housing portion 21 andfurther secured to the inside of the aperture through the main bodymember '16. The inner end of reflector housing portion 21 is secured asby brazing into the other end of the aperture through main body member16 so that a resonator cavity is formed within the main body memberdefined by the conical dish 15, drift tube 14, grid 17, ring 19, grid18, and the inside or side wall 10 of the aperture through main bodyportion 16. The

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reflector button 22 is supported by a cylinder 23 positioned withinreflector housing 21. The main body member 16 is provided with an irisopening 26 and vacuum seal window 26' to provide an exit into aresonator 25 for energy developed by the klystron. A flange 27 isprovided on resonator 25 for connection to the load circuit.

Positioned within a pair of aligned internally threaded apertures in thelegs L and R of U-shaped body member 16, as best seen in FIG. 3, is athreaded tuning stud 31. Tuning stud 31 is captured within =leg L ofmain body member 16 by the threaded aperture therein and captured withinleg R by an internally and externally threaded dif ferential tuning nut32 which is in turn captured by the threaded aperture in leg R.

When it is desired to change the oscillation frequency of the presenttube the mechanics of tuning are as follows. The tuning screw 31 islocked to the left leg of the body by a lock or jam nut 33. Then thedifferential screw 32 is turned thereby pulling together the legs ofmain body member 16. As this pressure is applied to the legs of body theround cavity is distorted due to a weakening of the base at 16' causedby aperture therethrough and becomes elliptical or egg shaped. Thisdeformation, as best seen in FIGS. 3 and 4 in turn forces the anodeheader 15 and the reflector header 19 to become more conical or to bowmore due to inward pressure and in turn moves the grid 17 away from grid18 as shown greatly exaggerated in phantom by FIG. 4. As the gap betweenthe grids 17 and 18 increases, the capacitance therebetween decreases,causing the frequency to increase. By turning the differential nut 32 inthe opposite direction the frequency may, of course, be lowered. It isfurther noted that the volume of the cavity will decrease slightly whendistorted thereby causing a decrease in inductance. The eflect of thiswill be to decrease the frequency and somewhat oflset the increase infrequency effected by increasing gap spacing. However, the increase infrequency due to the increased gap spacing will greatly overcome thechange in inductance due to the reduced inductance and the reduction maybe neglected.

Here is shown a rugged tunable reflex klystron suitable for utilizationin most severe conditions of environment. It is rugged enough to preventany change in frequency, or 'l megacycles stability) and further issufficiently rugged to greatly reduce rnicrophonics generally found ingap-tuned reflex klystrons.

Since many changes could be made in the above construction and manyapparently widely different embodiments of this invention could be madewithout departing from the scope thereof, it is intended that all mattercontained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. In an electron discharge device, a cavity resonator including aninteraction gap defined by a pair of mutually opposing grid members,support means supporting said grid members, said cavity resonatorincluding side walls to which said support means are secured, meansmounted on said electron discharge device for distorting portions of theside walls of said cavity resonator thereby distorting said supportmeans in such a manner that the spatial relation between said opposinggrid members is changed thereby effecting a frequency change of thecavity resonator.

2. The apparatus according to claim 1 wherein said support means includeat least one outwardly dished member, said outwardly dished memberbowing outwardly in variable accordance with the amount of distorting onsaid side walls.

3. The apparatus according to claim 2 further including an apertured,U-shaped member, the wall portions of said ferential tuning screw'is'threadedly captured by apertures in the legs of the U-shaped mainbody member to provide means for applying force to the lever arms fordistorting the side walls of the cavity resonator.

5. In a high frequency apparatus including a tunable cavity resonator,said cavity resonator having a re-entrant portion and including a gapspacing for electromagnetic interaction with a beam of electronspassable therethrough, said cavity having side walls and end walls, atleast one end wall being provided with an outwardly dished portion, saidoutwardly dished portions supported by the side walls of said cavityresonator, means for applying a force on the side walls to distort saidside walls, the distortion in said side walls acting on said outwardly,dished portion causing them to bow in such a manner that the gap spacingis varied in variable accordance with amount of distortion in the sidewalls.

6. In an electron discharge device, a U-shaped member including anapertured base portion, the walls of the aperture within said baseportion defining side walls of a cavity resonator, saidcavity resonatorincluding an interaction gap defined bya pair of mutually opposing gridmembers, support means for supporting said grid members, said supportmeans including at least one outwardly dished member, said outwardlydished member being supported by the walls of said cavity resonator, thelegs of said U-shaped member including a dilferential tuning screwthreadably captured by aperatures therein, said differential tuningscrew providing means to apply force to the U-shaped arms, said U-shapedarms acting as lever arms to distort the side walls of said cavityresonator, the distortion in the side walls of said cavity resonatorapplying force to said outwardly dished member thereby causing saidoutwardly dished member to bow in variable accordance with the amount ofdistortion in said side walls thereby changing the spatial relationbetween opposing grid members, said spatial relation efiecting afrequency change of the cavity resonator.

7. In a tunable high frequency electron discharge device, a tunablecavity resonator, said cavity resonator being defined by a pair ofspaced end portions interconnected by side wall portions, said endportions having a pair of aligned apertures for passage of a beam ofelectrons through said cavity resonator for electromagnetic interactionwith the electric fields of said cavity resonator,

said cavity resonator having a reentrant wall portion projectiongenerally inwardly of said resonator to concentrate the electric fieldsof said resonator and define an electromagnetic beam-field interactiongap in the path of the electron beam passable through said resonator,means coupled directly to the side wall portions of said cavityresonator for applying force on the side wall portions of said cavityresonator to distort said side wall portions, the

distortion'in said wall portions movably acting on said re-entrant wallportion causing said re-entrant wall portion to move in such amannerthat the gap spacing is varied in variable accordance with theamount of distortion in the side wall portions.

8. The apparatus according to claim 7 wherein said means coupled to saidside wall portions includes a pair of lever arms secured on the externalportion of said cavity resonator to which force. is applied to distortsaid side walls.

9. The apparatus according to claim 8 wherein screw means are threadedlycaptured by threaded apertures in the free ends of said lever arms toprovide means for applying force to the lever arms for distorting theside walls of the cavity resonator.

-10. The apparatus according to claim 9 wherein portions of said sidewalls are relatively thin with respect to adjacent portions of said sidewalls to allow distortion ofsaid side walls at the thin portionsthereof.

References Cited in the file of this patent UNITED STATES PATENTS CanadaJan. 30, 1948

